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University of Wisconsin Garden Facts
XHT1002
Chlorosis
Brian Hudelson, UW-Madison Plant Pathology
What is chlorosis? Chlorosis is a common nutritional disorder of many woody ornamentals in Wisconsin,
particularly in the southern and eastern parts of the state. Pin oaks are most commonly affected by chlorosis,
although many other trees and shrubs (e.g., white oak,
red maple, white pine and Rhododendron spp.) are
also very susceptible.
What does chlorosis look like? Symptoms
of chlorosis are easy to distinguish from those of other
diseases. Affected leaves turn yellow, except for the
veins, which remain green. In severe cases, foliage
may turn brown and die. Symptoms can occur on
isolated branches, or over an entire tree.
What causes chlorosis?
Chlorosis occurs
when a tree or shrub is lacking certain micronutrients,
in many cases iron or manganese.
Lack of
micronutrients in a tree may reflect a lack of these
nutrients in the soil due to poor fertility. Often,
however, there are sufficient micronutrients in the soil,
but they cannot be absorbed by a plant’s roots. Poor
absorption of micronutrients is common in Wisconsin
because of the high pH (alkalinity) of many soils.
How do I save a tree or shrub with
chlorosis? Chlorosis is rarely fatal and can be
treated. For treatments to be effective, you must
determine the exact cause of the chlorosis. Have the
soil around an affected plant tested for micronutrients
and for pH prior to applying any treatment. If the soil
test indicates a lack of specific micronutrients, fertilize
with these micronutrients. For example, chelated iron
Yellowing of foliage characteristic of
compounds can be used to increase the amount of iron
chlorosis.
in soil. If the soil test indicates a high soil pH, lower the
pH by applying sulfur or ammonium sulfate (see
University of Wisconsin Garden Facts XHT1151). Contact your county Extension agent for information on soil
testing, and for details on a treatment once you have determined the specific cause of your chlorosis problem.
How do I avoid problems with chlorosis in the future? Plant trees and shrubs that are less
susceptible to chlorosis, and make sure your trees and shrubs receive sufficient water (approximately one inch
per week). This will help plants with micronutrient uptake. If rainfall is insufficient, use a drip hose or soaker
hose to apply supplemental water. Remove turf from around the base of a tree and shrub out to at least the drip
line, and apply shredded hardwood, pine or cedar mulch in this area to help keep the plant’s root system moist.
On heavy clay soils, use three inches of mulch. On other soils, use three to four inches of mulch. Be sure to
keep mulch two inches from the main trunk of a tree. If you decide to plant susceptible trees or shrubs, watch
them closely for yellowing characteristic of cholorosis and apply corrective treatments as soon as
symptoms appear. Treatments should always be based on the results of soil micronutrient and pH tests.
For more information on chlorosis:
See UW-Extension Bulletin A2638 (available at
http://learningstore.uwex.edu) or contact your county Extension agent.
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Revised
Jan. 8, 2012
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Thanks to Sharon Morrisey, Patti Nagai and Ann Wied for reviewing this document.
A complete inventory of University of Wisconsin Garden Facts is available at the University of Wisconsin-Extension Horticulture website: http://hort.uwex.edu.